Some of the files were created using cp --reflink to save space. When I try copying with cp, this deduplication is not preserved. --reflink=always fails, reporting "Invalid cross-device link"

 

Both disks are single disk BTRFS (LUKS). You can see the difference in the size on disk for the domains directory I copied below:

root@server:/mnt/cache# cp -a --reflink=auto /mnt/disks/ssd/domains /mnt/cache/domains

 

 

Edited December 25, 20205 yr by golli53

If they are on a subvolume you can make a snapshot than send/receive to the other disk, if not create one and move data inside it first.

9 minutes ago, johnnie.black said:

If they are on a subvolume you can make a snapshot than send/receive to the other disk, if not create one and move data inside it first.

Gotcha - thanks @johnnie.black!